Photosensors have been widely used in various portable information products, such as notebooks, still cameras, video cameras, mobile phones, and the like. Normally, a product using photosensors typically includes a display device such as a liquid crystal display, which can be considered as being part of a display system of the product.
FIG. 3 is a block diagram of a typical display system 1. The display system 1 includes a micro processor unit (MPU) 11, an image sensor 14, a digital signal processor (DSP) 12, and a display device 13.
The image sensor 14 includes a number of photodiodes (not shown). When light irradiates each photodiode, a current is generated according to the intensity of the light, and the current is then provided to the DSP 12. The DSP 12 transforms the current into an image signal and provides the image signal to the display device 13. The MPU 11 is configured for initializing the DSP 12 and providing operational parameters to the DSP 12. When the process of initializing the DSP 12 is completed, the DSP 12 generates a startup signal and provides the startup signal to the image sensor 14. Parameters provided to the DSP 12 may represent a type or a size of the display device 13.
Normally, the DSP 12 includes some standard circuits (not shown) integrated therein, such as an analog-to-digital converter, a digital-to-analog converter, a filter circuit, an amplifier, and a compressor circuit. Thus the cost of the DSP 12 is high, and the cost of the display system 1 using the DSP 12 is correspondingly high. Furthermore, the display system 1 may not necessarily use all the circuits of the DSP 12. In such case, the display system 1 is unduly complicated and costly.
It is desired to provide a display device which can overcome the above-described deficiencies.